you need a program called tripcode explorer, however, its not as simple as it may sound.
if the word you're looking for is too obscure, it may not work.
what you need to do is think of a cool word that you want, click on start, and leave it running in the background. the list will slowly start to fill up with tripcodes that have the word you typed.
I made my code by typing "cirno" and letting it run in the background for a while